AGie AT MATURITY OF THE PACIFIC COAST SALMON II 
all those examined by us were males, with one exception, a female with well-developed 
ova. Examination of the scales (see pi. i, fig. i) shows that the final summer’s growth 
is more extensive in grilse than in those which mature at 4 and 5 years, and the 
narrowing of the marginal rings to form the third winter band has often begun. 
Much larger specimens than those included in the table were selected for examina- 
tion in an attempt to find individuals older than 5 years. Several were found over 
30 inches long, weighing 12 pounds, but all were 5-year fish. Examination of a larger 
number may possibly bring to light a rare individual which has not matured until its 
sixth year. Even this is doubtful and we assuredly do not anticipate finding older 
than 6-year individuals among the Eraser River sockeyes. The significance of the mark- 
ing experiments of the Bureau of Fisheries in the Naha River, with the reported 
recovery of marked specimens up to 9 years old, remains to be determined. 
If it be true, as indicated in our table, that relatively so large a proportion of Eraser 
River sockeyes mature in their fifth year, it may appropriately be asked how the enor- 
mously increased run every fourth year can be maintained in that river without its 
benefits becoming gradually distributed through five-year individuals over the inter- 
vening years. The great run of 1909 must have developed as 4-year fish from the 
superabundant eggs deposited by the great run of 1905. But if an almost equal propor- 
tion of those eggs should fail to mature until their fifth year, as was true in the 1911 
run which we investigated, we should have expected a second great run, characterized 
by their relatively large size, in 1910. Such increased runs in the fifth years do not 
occur, and of this we have as yet no explanation to offer. There is some evidence that 
the fifth years of the cycle are characterized by fish of somewhat larger size than the 
other “off years,” indicating, if true, a larger proportion of 5-year fish, but the total 
run is not appreciably increased. Certain it is that the fish of the big runs average 
smaller than those of the intermediate years. This might conceivably be explained 
by a limited food supply and sharper competition among the enormous schools of that 
year, but it is more probably due to the practical elimination of 5-year fish. Those 
5-year fish present would have developed in their due proportion from the few eggs of 
an “off year,” and would be too scattered to produce any effect among the vast hordes 
of 4-year olds. But these are matters for further investigation. 
KING SALMON, OR CHINOOK ( Oncorhynchus tschawytscha ) . 
[PI. iv-vii: fig. 15, pi. vm: pi. ix; fig. i8, pi. x; fig. 25. pi. xiv.] 
Speculation concerning the age of the king salmon (also called spring salmon, tyee, 
Chinook salmon, Sacramento salmon) has been encouraged by the enormous range in 
size which is exhibited by spawning fish. Adult females have been reported as small 
as 5 pounds, and adult sea-run males much smaller than this, while individuals of from 
80 to 100 pounds weight occasionally are seen. No answer has heretofore been given to 
questions concerning the total range in years represented by these various sizes, nor as 
to the exact relation of age and size. 
A detailed experiment to determine these points was undertaken by Superintendent 
Hubbard of the Clackamas (Oreg.), station, in 1896. Five thousand young, hatched 
